Rename computed array macros to match #3158

[mmun]

Renamed Ember.computed.mapProperty/Ember.computed.filterProperty to Ember.computed.mapBy/Ember.computed.filterBy and added deprecations.

[cibernox]

I think that mapProperty and filterProperty should remain as is.
At least for me the name mapByProperty seems that will return an array with the objects instead of an array with the properties.
And filterByProperty is even more confusing to me.

[hjdivad]

Consistency is a virtue. mapBy is what's on Ember.Enumerable so it's the right thing for the array computed macros.

Thanks for cleaning this up @mmun. ^_^